12. Synoptic chart interpretation Wind direction and speed The closer the isobars, the greater the speed. Wind speed indicators are attached to the symbols showing wind direction. Winds are named after the direction that they come from. E.g. A wind coming from the South is called a Southerly. Wind direction is determined heaps by the location of Pressure systems. In the Southern hemisphere winds blow out in an anticlockwise direction from areas of high pressure. The winds associated with low pressure systems blow in a clockwise direction towards the centre. Pressure systems These are defined by the patterns formed by the isobars. High pressure systems are indicated where barometric pressure increases towards the centre of a set of enclosed isobars. Low pressure systems are indicated where the barometric pressure decreases towards the centre. Fronts and rainfall Cold fronts These are formed when a mass of cold air moves in and displaces warmer air. The resulting uplift of warm moist air means that the passing of a cold front is often associated with rainfall. Warm fronts These occur when a mass of warm air moves in and displaces cold air. Areas in which rainfall has occurred in the previous 24 hours are highlighted by shading.
Wind direction and speed
The closer the isobars, the greater the speed. Wind speed indicators are attached to the symbols showing wind direction.
Winds are named after the direction that they come from. E.g. A wind coming from the South is called a Southerly. Wind direction is determined heaps by the location of Pressure systems. In the Southern hemisphere winds blow out in an anticlockwise direction from areas of high pressure. The winds associated with low pressure systems blow in a clockwise direction towards the centre.
Pressure systems
These are defined by the patterns formed by the isobars. High pressure systems are indicated where barometric pressure increases towards the centre of a set of enclosed isobars. Low pressure systems are indicated where the barometric pressure decreases towards the centre.
Fronts and rainfall
Cold fronts
These are formed when a mass of cold air moves in and displaces warmer air. The resulting uplift of warm moist air means that the passing of a cold front is often associated with rainfall.
Warm fronts
These occur when a mass of warm air moves in and displaces cold air.
Areas in which rainfall has occurred in the previous 24 hours are highlighted by shading.